1. Field of the Invention
This invention relates to improvements in electrical sockets, and more particularly to improvements in sockets for receiving the leads of an electrical component, or the like, for connection with leads of a printed circuit board, or the like.
2. Description of the Prior Art
With recent emphasis towards miniaturizing and microminiaturizing the physical size of electrical circuits, one of the principal structures employed to carry and support integrated circuit packages are printed circuit boards, formed generally of an insulating substrate, such as plastic, fiberglass, or the like, upon which conductive strips or leads are plated, etched, or formed, to function as interconnecting conductors between the desired electrical components.
Typically the conductive leads of such boards are designed to present a pattern for convenient physical location of the elctrical components to be mounted. The leads of the components, such as resistors, capacitors, transistors, integrated circuits, and the like, are ordinarily mounted in holes formed through the substrate of the board, usually at a terminal or intermediate location along an appropriate electrically conducting strip on the board. For good electrical contact to the component lead, frequently the holes are plated with a conductive material within the substrate, and the inserted component lead is soldered or physically attached to make electrical contact with the associated board lead. The holes are usually located by the circuit designer at the locations necessary for receiving connections to the appropriate component leads. For example, if a resistor is to be mounted onto the board, the two holes for receiving the component leads of the resistor can be located at a spacing somewhat larger than the length of the resistor to enable the resistor leads to be bent and inserted through the holes. Likewise, to receive the leads of a transistor, three holes may be located in an aligned configuration or in a triangular configuration, depending upon the configuration of the leads extending from the transistor device itself. The particular locations, therefore, of the component leads and their associated component lead receiving holes are, for the most part, arrangeable for the particular application desired.
For further ease in the mounting of components, especially multilead integrated circuits and the like, onto printed circuit boards, frequently individual component lead receiving sockets are mounted onto the board within the preformed holes, for instance, one socket per hole, to receive a single component lead. Usually such individual lead receiving sockets are hand mounted onto the printed circuit board by inserting a portion of the individual socket into its respective hole, and hand soldering it into the inserted location. The hand soldering and hand mounting of the individual lead receiving sockets involves detailed, time consuming work, which detracts somewhat from the desireability of including the sockets in the first place-the time saving convenience in locating and establishing electrical connection to the components on the printed circuit board. On the other hand, the individual lead sockets can be machine mounted, if desired, but such machines are ordinarily large and require large capital investments, which may not be appropriate in many printed circuit board fabrication facilities.
Alternatively, a number of individual lead sockets can be premounted into a single socket unit. This is typically done by forming a header or a base and hand or machine mounting the desired number of individual lead receiving sockets into it. Such mounting of the individual lead sockets into the header is usually done by hand or by specially designed equipment, again often undesireably requiring large capital investments. The base containing the individual sockets can then be mounted into a corresponding series of holes formed on the printed circuit board in a configuration suitable to receive the particular connection or pin configuration displayed by the header or socket unit and soldered by hand, machine, or otherwise, into place. For example, wave soldering techniques are commonly employed to achieve such solder connections to the printed circuit board; however, with most such socket units (and with the individual lead sockets themselves mounted directly into the board), particular care must be taken to prevent excess solder from flowing by capillary action or otherwise over the lead receiving opening of the individual sockets to clog or obstruct the sockets or to interfere with the subsequent insertion of the component leads.
With the printed circuit board and the premounted socket units thus fabricated; the leads of the components can be subsequently easily manually inserted into the appropriate socket to complete the assembly of the unit. Nevertheless, such discrete socket units are usually of realtively large size, the base or header being made of bakelite, plastic, or the like, molded into the desired configuration to contain almost the entire structure of the individual lead receiving sockets. This results in the entire structure of the individual lead sockets being located above the surface of the board, thereby increasing its physical dimensions. Also, because the header units are molded, it is apparent that repairs to the mold or die structures or the the individual socket inserting equipment can be particularly costly, and, in small scale manufacturing operations, may not be warranted by the number of units to be produced.
Another disadvantage in such discrete header or socket installations is that the manufacturing tolerances of the holes of the printed circuit board for receiving the leads of the socket units must be carefully controlled. A misalignment, for example, either in the spacing location or in the angle of the center line axis of the holes may prevent the socket from being insertable at the intended location, requiring special attention to complete the fabrication of the board, if possible at all.